In general, in recent years, a technology for copying a data between information processing systems and maintaining the duplication thereof in order to maintain a data and a service even in the case where failures develop due to disasters and the like in the information processing system to maintain the data. As such a technology, there is the technology, which performs the remote copying of a data between remote sites having a storage apparatus respectively and maintains the duplication thereof. For example, as a state, the side which maintains a duplication object data is taken as “original (primary)”, and the side which maintains a duplication is taken as “duplication (secondary)”, and a duplication data (secondary user data) on a user data (primary user data) maintained by the primary storage apparatus of the primary site is maintained at the secondary storage apparatus of the secondary site.
As for a technology for duplicating the data, in a data duplicating system initiated by a primary host computer, when updating the user data, it is necessary to write an update data on both the primary and the secondary storage apparatuses from the primary host computer. Consequently, even in order to carry out the service for the users (business enterprises and individuals), a load of the primary host computer such as an increase in the number of I/O (input and output) processing accompanied by the data duplicating, a pressure given to the memory bus of the primary host computer and the like becomes large.
As a technology for performing the copying of the user data and maintaining the duplication thereof between the primary and secondary sites in the data processing system where the information processing systems having the host computer and the storage apparatus respectively are disposed at remote sites, there are a remote copy processing system (hereinafter referred to as a storage base copy) initiated by the storage apparatus and a remote copy processing system (hereinafter referred to as a secondary host base copy) initiated by a secondary host computer, on which the present inventors have worked extensively as a prerequisite technology of the present invention.
With respect to the storage base copy between the primary and secondary sites, when the storage apparatus updates the primary user data from the primary host computer, an update data (a data written on an update position in the primary user data) received from the primary host computer is directly remote-copied for the secondary storage apparatus through a communication link between the primary and secondary storage apparatuses, and by allowing the update data to be reflected on the secondary user data, a data synchronization of the primary and secondary user data is performed. In this processing system, there is no load of the primary host computer accompanied with the processing of transferring the update data of the primary user data in the primary site to the secondary storage apparatus and reflecting it on the secondary user data.
With respect to the secondary host computer, the secondary host computer reads (copies) the update data of the primary user data in the primary storage apparatus by a remote through the communication link between the primary and secondary sites, and by allowing this update data to be reflected on the secondary user data of the secondary storage apparatus, the data synchronization between the primary and secondary user data is performed. In this processing system, since the primary host computer does not need to coordinate with the processing of transferring the update data of the primary data to the secondary site side and reflecting it on the secondary user data, there is no load accompanied with this processing. In the specification of the U.S. Pat. No. 6,052,758, there is disclosed a technology corresponding to the secondary host base copy.